When using RSTP, which condition makes a port enter the Learning state?

The condition that allows a port to enter the Learning state in Rapid Spanning Tree Protocol (RSTP) is when the port starts to process frames but does not yet forward them. In the Learning state, the switch learns MAC addresses by inspecting the source address of incoming frames in order to build the MAC address table. However, during this state, the port does not forward frames to ensure that network loops do not occur.

When a port is in the Learning state, it is preparing to transition into the Forwarding state, where it will actively send and receive frames, but it first needs to gather the necessary information about the MAC addresses in its environment. This step is vital to ensure an efficient and loop-free network, allowing the switch to quickly adapt to topology changes while maintaining network stability.

Other conditions mentioned, such as a port actively forwarding frames, mean that it is already in the Forwarding state, which comes after Learning. When a port neither receives nor sends frames, it usually indicates that the port is in a different state, such as Blocking. A topology change typically triggers the spanning tree process to reevaluate port states, but it does not directly cause a port to enter the Learning state; rather, this is a separate process involved in responding